<?php
    $array = array();

    $array['a'] = 'a';
    $array['b'] = 'b';
    $array['c'] = 'c';


    function test(&$a,&$b,&$c){
        $a = 3;
    }

    $values = array_values($array);
    $keys = array_keys($array);
    test(...$values);

    for($i = 0; $i < count($keys); $i++){
        $array[$keys[$i]] = $values[$i];
    }

    echo $array['a'];
?>